Car and Driver: Active vs. Standard Suspension

[Jesda]

This is a Car and Driver article from Wes that I scanned. Interesting comparison.

http://www.q45.org/active/

[CrimsonQ]

nice article. Thanks for tossin it up

[szh]

Interesting!

According to the car, about 11% of the Q's sold had the active suspension ... I wonder how many are still that way and running anywhere close to the original design target!

Z

[Q45tech]

So ~~1500 [91a were sold] there must be 2 or 3 in US still functioning near new.

The interesting part was no increase in peak numbers [due to added 200 pounds on the same tires...................would be interesting to try the same test on stronger higher load index tires as soft as oem.

In theory the 0.77G [300ft slalom] could go up by 1/2 the percentage gain of tires over 1521 max load..............1640/1521= 1.078........1.039 x 0.77= 0.80G assumng same fast wear stickiness.

The [active] rear sway bar was used up dealing with the extra rear 100 pounds swaying.................what I've found on my Q when I load my trunk with 150-200 pounds. 40 extra pounds per roll inch isn't much added stiffness compared with 123 stock [non active]..... [88 active].

Based on the recent tires I've seen on Q45a they probably have a tough time getting to 0.70G even 0.65.

[Q45tech]

The other interesting chart was how linear the body roll [in degrees 0-6] was per 0.0G-0.8G of lateral on the standard Q.............Soft springs.

The ratio of pitch vs 0.75-0.9G braking {{1.6 degrees}} v 5-5.8 degrees in body roll for same load 0.75 G lateral proves the benefit of adding a rear sway bar to standard Q.

This needs studying closely as there is a wealth of potential in modifying these numbers.......the question is where to get tires that approximate those used as new.

[Jesda]

Uh, yep.

[szh]

Good info, Dennis!

Z

[szh]

Uh, yep.

ROFL!

There is a quiz tomorrow at 9am.

Z

[Rex]

What I got from Dennis' posts was something I think we've all been learning over the years ... tires are the biggest impedance to performance.

[elwesso]

it would be interesting to compare under the similar conditions with max performance tires (bridgestone RE050a or PS2) .. see if that really makes any difference.....

The active really is seeming like something that id rather not deal with... especially after working on ross's Q

[Falkdesigns]

You'll also note that all the diagrams have the standard Q soo freakin' close to the A. IMO, the reason they didn't bother keeping it alive, and why no one else in the world has either, is that with good shocks, springs and tires, the advantage -which is minimal in some areas, and worse in others (slalom, g's,...)- is not worth the $$$$$.

Nice read though!

[Q45tech]

The $8-10,000 increment [20-10%] was not the problem on a new lux limo for the President of a company to be driven around.............ride and brake dive important.

The problem is buying a worn out ----post 60,000 mile unit.

Read a study on Dell's low cost color laser printer [$300].............when it runs out of 4 color ink you throw the whole unit away.............as replacements carts and drum costs 70% of the unit.................10 cents per page.

GM is promoting its new Magna drive ..........magnetic fluid shocks as the fastest reacting system around.........they draw 12 amperes plus per shock.......something will give in the power control alternator system after a few years.

Bring it in for a bad ride and you are sold a new battery and alternator and a few thousand worth of control modules at 50,001 miles

Back to Q45a: The reason the stock Q does so well is the front twisted/angled upper link which compensates for camber during body roll [at the expense of tires] and fast wearing of the link isolation rubber.

Notice the Q45a works hardest up to 0.4G lateral.........then begins to track linearly...........so one would not expect improvements at the limit...........too dangerous when tire friction falls below 0.4 in cool wet weather.

If they had tried to significantly increase peak G the tires wouldn't last 2,000 miles instead of the nominal 15,000.

Hard to get people to understand that tires are 86% and suspension is 14% in equal weight situations.

Look at Tire Rack tests on lowering springs and sway bars........2,2.5,3% improvements at best on BMW...........when its close to RIGHT, it is Right.

Something to consider is: what was the built in camber compensation for the 215/65/15 tire..............with lower aspect ratio tires and the same body lean..........the system [active or standard] may provide too much negative camber overshooting the "sweet spot"..................so you must limit body lean when you go to 55,50,45,40 tires.

The 6 degrees should be reduced by 1-2...............15-33% stiffer springs.

Study sidewall roll stiffness specs of tires you buy.

[anniversary ed]

Hi this Rover under a new name as I could not re-set my password

Not wanting to high jack the thread I thought I would repost the info I found on the Y33 with active struts and my comparison to driving a Q45A, standard Y33 and the Y33 with the adjustable suspension.

Y33 ADJUSTABLE SUSPENSION DESCRIPTION

Also new for 1999 is an Active Damper Suspension, available as standard equipment on the Q45t. This system offers electronically modulated shock valuing control with SPORT and AUTO driver selectable settings.

The system uses real-time, independent 4-wheel shock absorber damping force regulation in response to input from vertical G-sensors and steering angle sensors. Signals from these sensors are sent to the system's computer control unit, then matched with vehicle speed. "Instruction" data is then sent back to actuators above each individual shock absorber, which immediately adjust shock absorber damping force.

The system helps eliminate excessive body movement, such as in hard cornering, braking or acceleration. It also helps improve tire-to-road surface contact for greater stability and enhanced handling control.

With the two adjustable settings, drivers can chose between a softer, more comfortable ride or a firmer ride with more road feel, depending on road surface, traffic and climate conditions or personal preferences.

HERE IS MY ASSESSMENT COMPARING THE ACTIVE Q I HAD, MY 1998 Y33 AND MY RECENT 2000 Y33 WITH ADJUSTABLE SUSPENSION

I took it on some winding country roads this evening which is an alternative route home from work. I used to take the active Q on this route as it is a great mixture of rough pavement, long sweeping curves, sharp 110 degree bends, hills and 3 stops. Here are my observations

Rough Pavement - Active Q - noisy but excellent bump absorption1998Q - Noisy, comfy but lots of body movement2000Q Anniversary - quiet, excellent bump absorption, body movement well controlled

Long Sweeping curves - ActiveQ completely flat inspire confidence very stable1998 - some roll evident limiting driver confidence2000Anniversary - almost no roll, inspires driver to press on in confidence

Sharp bends - Active Q - virtually no roll unless G force exceeds 0.5 inspires driver to really push, tires limiting factor1998Q - roll quite evident not a lot of fun and tends to cause driver to back off, tire limit not reached2000Anniversary - amazing really very little roll inspires driver to push,tires eventually squeel but can feel car really dig into the corner. Lots of fun feels very sporty

Sharp stops - Active Q no dive incredible feeling1998 Q lots of dive2000Anniversary - some dive but very much reduced compared to 1998

[ceningolmo]

Hey now! Easy on my Q... it may not be the finely tuned piece of machinery that yours is... but, its mine and I like it.

Besides... you know once I get all the "other crap" done and you get the chance to start tinkering with the active, you are gonna love it.

[elwesso]

Rover email me and we'll get you taken care of.

[elwesso]

Not saying its "crap", just saying for what it actually does, its a little too complex for me... not to say I couldnt handle it, but paying $260 for a set of shocks does seem pretty

[Q45tech]

Remember shocks only control the rate of change in transistions.

They have nothing to do with peak steady state handling.

The tire, the weight on the tire, and the tires camber angle........how well the suspension geometry holds the tire contact patch at negative 0.5 degrees camber at that specific cornering load.

Suspension are never perfect, they are preset to approximate what ever camber compensation is required to match a specific tire in a specific size.

Change tire brands and they are always different.

[elwesso]

Tech maybe im having a hard time following you but it seems as if the optimal camber is at -0.5*at any given cornering load... Maybe that is not correct.. Since camber gain is linear and directly proportional to ride height, would it be correct in stating that due to the lack of body roll in the active Q and due to the camber gaining nature of the Q45 multilink suspension that there is not ENOUGH camber being gained.....

so when you have the car at full cornering you want the tire bearing the load (the passenger side on a left turn) to be at a true -.5* camber.... assuming you use a OEM 215-65-15..... If you used, say a 245-45-17 you would want LESS camber... so if you had a way to adjust this camber [stillen or SPL upper links] assuming stock ride height, you would want to INCREASE (thus decreasing static negative) camber....... so that you maximize your tire contact area...

so in the case of the active Q, would it be beneficial to stligtly increase negative camber??

Back to the stock Q with lowering springs, you woud in theory want to start out with a more negative camber since you are starting lower...

[DuDro]

Is the "Active Damping" system in the F50 a refinement of the "Active" system in the G50?

[Q45tech]

No the newer system is just an on off switch to make shocks stiffer! It's active in the sense that the car decides whether to do it or not.

No self leveling or antidive in braking.

When you have shorter stiffer sidewalls there is less tire positive camber gain in cornering so you need less negative camber gain in suspension design to try to maintain the correct tire camber.

[Q45tech]

Based on the 5.8 degree body roll for 0.8G graph of no rear sway bar Q [123 lb/in rear springs it appears you would have to double the rear stiffness to half the body roll. From the graph the 20mm [with rubber bushings] reduces roll to 4.6. About 25% on the 5% heavier rear section.

The mathematics roughly correlate 30% stiffer rear yields 25% less with 5% more weight. So on a non active 30% stiffer should yield 30% less roll.

With progressive Eibachs the spring rate goes up by 30% [110 >150>200] at 3" so that should be additive.

For sure the two sum to 50% maybe 60%............my guess is the resultant is a ~~3 degree rear body roll.........half the stock Q and nearly ideal. And significantly better than the 4.6 degrees of the active.

To maintain balance the front sway bar engagement [rubber bushing compression] must be tuned to allow 5-10% more roll on the front since the weight is higher there...........the 15% stiffer front Eibachs and the 15% softer 28 mm bar means the bar engagement must be 25-30-35% faster........less slack in bushings. to simulate stiffer springs.

Obviously in braking the 15% stiffer front springs act like 30% together so brake dive is reduced by 30% from 1.6 degrees to ~~ 1.1 degree still 2.75 times more than the active dives but tolerable. There might be a tiny betterment with brand new Tokico Blues as they are stiffer by 15% at least in the 1st second of braking.

The braking distances were equal between active and standard so the antidive did compensate for the 5% etra weight.

Unfortunately they didn't give us alignment numbers for each vehicle so some of variances or betterments could be from different alignments!

[louiegz]

I think where most are missing the point on the active is the every day driving experience is improved. The Q wasn't meant to be taken to the limit. A while back, my friend bought a Passport G timer and I tried it on my car to do some 0-60 runs. When your not timing yourself, it gives you real time G reading on acceleration, braking, and turning. During some semi spirited driving, I barely cracked .5Gs, so for most driving situations, the active fits the bill. Sure the standard Q has more grip, but how often are you going to be there in a 2 ton luxury sedan. I think an active system is essential in a car the size of the Q to not have boatloads of roll on you're average right hand turn in the city, while still remaining soft on the straightaway over potholes and bumps. As we know, the problem with the active system is the complexity, expense and weight. Hell, if Texasoil lived closer to me, I'd love to have an active Q, but I don't have the skills or the time to be pulling out accumulators, sending them to Texas and reinstalling them. If you start to stiffen up the standard Q with lower springs, rear sway bar and poly bushings, you get a sharper handling car, but a bit of a rattle box on the bumps. Hell, even my Q, when I added the rear sway bar, I notice the harshness over bumps with not much gains in the handling department.

I was on the Koni website the other day and I was reading about these new Koni FSD shocks that looked interesting.

http://www.koni.com/FSD/

The FDS stands for Frequency Selective Damping. They claim that by the frequency of the road, it adjusts the oil flow in the shock to adapt to driving condition. If this works, this would be great. You'll never see it for the G50, but I'll look into these when it's time to change the shocks in my E46.
Modified by louiegz at 12:27 PM 4/6/2006

[DuDro]

No the newer system is just an on off switch to make shocks stiffer! It's active in the sense that the car decides whether to do it or not.

No self leveling or antidive in braking.....

The following quote comes from Infiniti's site about the Q45/F50:

"REFINE YOUR LEVEL OF PERFORMANCE: Infiniti's Active Damping Suspension uses an array of sensors and a central computer to deliver a ride quality that's smooth yet sporty. It adjusts each individual shock absorber in response to the Q45's actual body movements to flatten the ride and minimize bumps. Depending on how you prefer to drive, it even allows to levels of adjustment: 'AUTO', which adjusts to your driving style, or 'SPORT' for firm, taut handling."

The site goes on to illustrate how the system reduces diving when braking and body roll when cornering.

So....what's the real story behind this system?

[Q45tech]

poly bushings the big no no if vibration and noise is a concern.

You can accomplish the same thing with harder [durometer] rubber just need siffer sway bars or a lot of time to fine tune system......took me man weeks to get the suspension where I liked it to be with rubber, lots of ordering and hand made pieces.

When I used the rear 24mm bar I HAD TO MAKE EVERYTHING, 10 RUBBER BUSHINGS. GOING BACK TO 20MM MADE IT EASIER.

[maxnix]

Infiniti's Active Damping Suspension uses an array of sensors and a central computer to deliver a ride quality that's smooth yet sporty. It adjusts each individual shock absorber in response to the Q45's actual body movements to flatten the ride and minimize bumps. Depending on how you prefer to drive, it even allows to levels of adjustment: 'AUTO', which adjusts to your driving style, or 'SPORT' for firm, taut handling."

The site goes on to illustrate how the system reduces diving when braking and body roll when cornering.

So....what's the real story behind this system?

Like it says, it actively adjusts the shock valving. The unsprung weight is still 100% borne by the springs.

Not the same as the hydraulically assisted semi-active struts fo the G50. The dynamic changes and some static load is borne by the active hydraulic struts. Most of the static load is borne by the springs.

[Aussie Q45a]

The active really is seeming like something that id rather not deal with... especially after working on ross's Q[/QUOTE]

Wes, It's just the fear of the unknown. Once you get into the Active system it's pretty straight forward. Sorting out what pressure to put into the Accum's is the hardest part. I started at 900 and am working my way up. Wish I lived in the USA as Keith would have my accum's in a flash!

The pic is with the controller set on high.

[Q45tech]

Look to the difference is springs: 88 vs 123 in rear [108 vs 146] in front to gauge that the active part supports ~~~25% of the weight.

Equal to the lateral transfer weight up to ~~~0.45 G.

Body roll or the lack there of doesn't doesn't change transfer weight materially.

In theory with a stiffer than 20mm rear bar [and swaping back to front 29mm bar vs 28] you could extend the G point where the active gives up.

Not sure anyone has tried this but it should work.........with stickier/stronger than oem tires.

Reprogramming software might be a challenge?

[elwesso]

The active really is seeming like something that id rather not deal with... especially after working on ross's Q

Wes, It's just the fear of the unknown. Once you get into the Active system it's pretty straight forward. Sorting out what pressure to put into the Accum's is the hardest part. I started at 900 and am working my way up. Wish I lived in the USA as Keith would have my accum's in a flash!

The pic is with the controller set on high. [/QUOTE]

You may very well be correct..... I am not doubting you at all.. This all goes without saying, that I would LOVE to own active Q45 someday, but not as a daily driver.... Somethign where I could piddle with it and not have to rely .

[Ozzie]

Wes, It's just the fear of the unknown. Once you get into the Active system it's pretty straight forward. Sorting out what pressure to put into the Accum's is the hardest part. I started at 900 and am working my way up. Wish I lived in the USA as Keith would have my accum's in a flash!

The pic is with the controller set on high.

I so need to come and visit you when I have some cash and get my active all tweaked up again!

[Q45tech]

" Since camber gain is linear and directly proportional to ride height, would it be correct in stating that due to the lack of body roll in the active Q and due to the camber gaining nature of the Q45 multilink suspension that there is not ENOUGH camber being gained....."

You are correct as the upper link angle [unit] is the same as standard Q upper link. Why the active is even worse on tires depending upon how you drive it.

Note the active has a smaller front sway bar 28 vs 29mm standard, this reduces the load transfer from the bar by 13%.........but the stiffer spring like action of the active washes this potential gain away.

The 120+ extra pounds on the front really stresses the tires by at least 5% more yet they didn't chose a stronger tire since none were available in the 215/65/15 size and Michelin has more safety reserve than other brands in the same size [usually except for special designs].

Not sure they expected the handling abuse US cars can get regularly because of the low average speed in Japan. Nor did they expect that owners would not spend the multi-thousands necessary to maintain as new performance.

Would be nice to see an active with Pilot Sports 255/245/17 and measure the same parameters..........with 29mm front and 24 mm rear bars and a SLIGHT desensititation of the G sensor to fool active ecu/controller that the G might be lower?